The present invention relates, in general, to a wedge shaped friction casting that serves as a shock absorber in the suspension of railroad cars and, more particularly, the present invention relates to a composition liner bonded to a backing plate for such wedge shaped friction casting.
The suspension of railroad trucks include a wedge shaped friction casting which serves as a shock absorber. The wedge is supported by a spring and works between the bolster and the side frame. The sloped face of the wedge maintains contact with a mating face of the bolster while the vertical face of the wedge slides against a metal wear liner on the side frame. The spring pushes on the bottom face of the wedge thereby providing the load to force the wedge between the bolster and the side frame. The friction between the wedge and the side frame wear plate provides damping for the truck suspension.
Certain truck designs use a wedge with a composition friction liner bonded to the vertical face of the wedge. This composition liner provides the desired friction characteristics, particularly static friction similar to dynamic friction. The difficulty encountered with this design has been in obtaining a satisfactory bond of the composition liner to the cast metal wedge. Various methods of gluing a molded sheet of composition material and of bonding the material to the casting have been used. Under the severe operating and environmental conditions of railroad service, the composition liner sometimes separates from the cast metal wedge.
The present invention, therefore, provides a friction wedge assembly for use in a suspension system of railroad car trucks. The friction wedge assembly comprises a cast metal wedge having a bottom face, a vertical face that is substantially perpendicular to the bottom face and a sloped face for contacting a mating surface on a bolster of such railroad car truck.
There is a metal backing plate that has a first side removably engageable with the vertical face of the cast metal wedge and a means for securing the metal backing plate to the cast metal wedge. There is further a composition liner disposed on a second side of the metal backing plate for engaging such metal wear liner on such side frame of such railroad car truck.
It is, therefore, one of the primary objects of the present invention to provide a composition liner with a backing plate for a friction wedge assembly to eliminate the need for bonding the composition material to the cast metal wedge.
Another object of the present invention is to provide a composition liner with a backing plate for a friction wedge assembly that can be replaced easily thereby renewing the wear surface without having to install a new wedge casting.
Still another object of the present invention is to provide a composition liner with a backing plate for a friction wedge assembly that will reduce the need for handling the heavy wedge casting.
Yet another object of the present invention is to provide a composition liner with a backing plate for a friction wedge assembly that will be easily made interchangeable with existing wedge castings.
Another object of the present invention is to provide a composition liner with a backing plate for a friction wedge assembly in which the bonding of the composition friction surface is improved.
It is yet another object of the present invention to provide a composition liner with a backing plate for a friction wedge assembly that can be installed without the need for special tools.
Still another object of the present invention is to provide a composition liner with a backing plate for a friction wedge assembly wherein the composition liner can be assembled to the wedge casting at any location.
Another object of the present invention is to provide a composition liner with a backing plate for a friction wedge assembly in which the friction wedge casting is cost effective.
Yet another object of the present invention is to provide a composition liner with a backing plate for a friction wedge assembly which will reduce maintenance.
These and various other objects and advantages of this invention will become apparent after a full reading of the following detailed description, particularly, when read in conjunction with the attached drawings as described below and the appended claims.